INDIANAPOLIS -- Perhaps not surprisingly, Tony Stewart turned down Roger Penske's offer of a ride in the 2013 Indianapolis 500.
Stewart announced his decision at the annual International Motorsport Industry Show, of which he is a founding partner.
"It was kind of heartbreaking here to hear the crowd so upset when we said we weren't going to do it," Stewart said last week at a reception at Lucas Oil Stadium opening the 2012 edition of the racing trade show.
"But it's like being at Thanksgiving dinner … my plate is finally full. I don't know that I could add any more to what I've got right now."
At the NASCAR Sprint Cup banquet in Las Vegas on Nov. 30, Penske surprised Stewart and the rest of the racing community with his offer to provide a car so the two-time Sprint Cup Series champion could "do the double" -- compete in the Izod IndyCar Series Indianapolis 500 and the NASCAR Sprint Cup Series Coca-Cola 600 in the same day.
Stewart, who raced Indy cars under Indy Racing League sanction full-time from 1996 to 1998, performed the double feat in 1999 and 2001. In the latter year, he finished sixth at Indianapolis driving for Chip Ganassi Racing and third at Charlotte in a Joe Gibbs Racing stock car.
Since then, the 41-year-old Indiana native has maintained that an IndyCar non-regular would have little chance of being competitive in a one-off outing, and Stewart repeated that mantra Wednesday in Indianapolis.
"The IRL is so competitive now, probably stronger than it's ever been as far as competition," Stewart said. "You're not going to stroll in there for the month of May and expect to be on the same page as those guys. You'd have to start the season from the beginning to become acclimated to the team you were going to run the month of May with.
"Roger and I never even spoke about it," he added. "It's a great opportunity, but it's very hard when you're running three [NASCAR Sprint] Cup teams right now -- the obligations we have with making sure we're doing the right things for Ryan [Newman] and Danica [Patrick], as well as Donny Schatz and Steve Kinser and Bryan Clauson and Bobby East. We've got a lot of people that depend on us. There's a lot of responsibility there, and since I've been a team owner I pretty much ruled out the possibility of ever running Indy again.
"So as much as I would like to do it, I just don't have the time to do it proper."
If Penske is serious about running a Cup driver in the Indianapolis 500, and if contractual conflicts could be worked out, the legendary car owner wouldn't have to look far for a competitive alternative.
Brad Keselowski, who just clinched Penske's first NASCAR Sprint Cup title (to go along with 12 Indy car championships and 15 victories in the Indianapolis 500), told ESPN.com that he would be interested in "doing the double" in the future.
"Ford doesn't have a presence in Indy car racing, but if they did, I'd be knocking on Roger's door and he'd be knocking on mine," Keselowski said.
"How could it not appeal to you? It would be the pinnacle achievement in motorsport of all time. If you could go out and win one of those races, let alone two, you'd be a legend."
IndyCar Series champion Ryan Hunter-Reay said he was disappointed that Stewart did not accept Penske's challenge.
"I was hoping to see it happen," Hunter-Reay said. "We want the best here and welcome anyone who wants to come drive in the Indy 500, especially with someone like Tony Stewart's qualifications.
"We want to race against the best and we want to win against the best."
Hunter-Reay noted that Stewart -- or any other driver from a series outside of IndyCar -- would have a difficult time adapting to the foreign machinery, even with more than a week of practice time available at Indianapolis.
"We've seen the IndyCar drivers go over and put their toe in the water in NASCAR and more times than not it hasn't looked very good," RHR said. "I really respect what those guys do with those heavy cars, big horsepower, little tires, and I'd love to try it if I had a competitive opportunity.
"On the other hand, they would have a steep learning curve here, too. We haven't seen anybody come over here, but I would welcome seeing a NASCAR driver jump in an Indy car. Somebody like Tony knows how to adapt to different race cars. He's talented, he's been around the block, so he could absolutely do it."
Prior to the establishment of the Brickyard 400 stock car race, NASCAR drivers sporadically competed at Indianapolis through the mid-1970s.
Bobby and Donnie Allison, Cale Yarborough and LeeRoy Yarbrough all made starts in the Indy 500, with Donnie Allison's fourth-place finish in 1970 standing as the best result.
Indy car drivers Mario Andretti (1967) and A.J. Foyt (1972) have claimed victory in NASCAR's biggest race, the Daytona 500.
In 1994, John Andretti was the first driver to complete the Indianapolis-Charlotte double. Stewart, in 2001, was the last.
